The present invention relates to an internal combustion fastener driving tool including a handle system that is coupled to and supports a drive system, a magazine, and a nose piece. The fastener driving system is operable through an internal combustion driven piston. The drive system includes a driver body which includes a piston housing in which a piston is slideably housed. A driving member is coupled to the piston. A combustion chamber is defined by the driver body, piston housing, and piston. The piston and driving member are axially arranged and configured within the piston housing to drive a fastener upon combustion of a metered amount of gaseous fuel in the combustion chamber.
A preferred piston includes a self-lubricating compression ring and a piston body. The self-lubricating compression ring is arranged and configured to be retained around the circumference of the piston body and to form a seal between the piston body and the piston housing. The self-lubricating compression ring forms a durable seal in the absence of added lubricant. A preferred piston housing comprises a generally cylindrical portion and a portion in the shape of a truncated cone. A preferred piston housing also comprises features such as a cylinder head and an accelerator plate.